1. Field of the Invention
This invention relates to a method for manufacturing cold-forged wing nuts, particularly to one having a column linear material rolled and compressed into a wing-shaped linear material first and then carrying out a series of processing steps including shearing, flattening, compressing and trimming, punching, forming of wings and threading, able to quickly produce wing nuts having high strength and corrosion resistance under a condition of producing less waste material. Particularly, one more step of forming insert grooves is added between the two steps of flattening and compressing-trimming to let each sheared material formed with insert grooves which, after the step of threading, is inserted therein with a nylon or metallic sheet and then fixedly riveted together to make up wing nuts able to prevent loosening whether temperature is low or high.
2. Description of the Prior Art
Generally, hexagonal and quadrangular nuts are most commonly used for the present because they can be manually screwed and unscrewed conveniently. Such nuts are widely applied to daily articles, such as the positive and the negative poles of a battery, a TV antenna, a collapsible bike and the like.
However, the conventional methods of manufacturing wing nuts have some defects described below.
1. The method of compressing thin steel plate into shape, as shown in FIG. 9A, has the following drawbacks.
(A). A metallic material used is comparatively thin so it is easy to split in the process of threading, resulting in many unqualified products.
(B). A nut body is not solid so it is liable to oxidize and corrode in case of being exposed outdoors. Especially, the two wings of the wing nut are most likely to be broken by turning around, giving rise to inconvenience in screwing and unscrewing.
(C). Compression formed, the nut body is easy to produce sharp hairy edges to cut and hurt a user's hand.
(D). In the process of compression forming, part of the metallic material may be wasted, thus wasting metal material and lowering economic gain.
2. Method of iron casting: Iron liquid is injected into a mold to be cast into shape, as shown in FIG. 9B. Although the nut cast in this way is solid, yet it has the following defects.
(A). The cast wing nut has a rough surface, having poor feeling of touch.
(B). The opening for injecting iron liquid forms a sharp notch in the surface of finished nut, likely to cut and hurt a user's hand.
(C). After cooled and shrunk, the cast nut is likely to produce stress concentration, rendering its two wings easy to be broken by a comparatively large external force.